Typical screen and storm doors available on the market have an existing closing device already associated with them. The existing closing device serves two main functions. Firstly, the closing device is biased so as to ensure that the door closes when it is not held open. The second function of the existing closing device is to ensure that the storm door does not slam shut when it is closing, but rather the door is caused to close slowly.
Existing closing devices essentially comprise a cylindrical tube, a piston-like member disposed in the cylindrical tube, biasing means forcing the piston-like member to one end of the cylindrical tube, and means for controlling the rate at which the piston-like member is forced to that one end.
In use, the existing closing device is suitably connected between the frame of the door and the door. As the storm door is opened, the shaft of the piston-like member is forced out of the cylindrical tube, thereby compressing the spring. When the door is released, the spring causes the piston-like member to return to its original location, thereby causing the door to close. The rate at which the door is closed is dependent on the rate at which the piston-like member is allowed to return to its original location.
Existing closing devices for storm doors can be fitted with a stopping means on the shaft of the pistonlike member. The purpose of the stopping means is to prevent the piston-like member from returning into the cylinder, thus keeping the storm door open. However, in order for the user to keep the storm door open with the stopping means, he must adjust the relative position of the stopping means on the shaft of the piston-like member, and ensure that the stopping means is locked in position.
There is a further disadvantage with the existing closing devices for storm doors. It is almost always the case that upon opening an existing storm door, the householder is left performing a juggling act to find keys, balance bags or parcels, while at the same time bracing the storm door open with a knee, elbow, hip or ankle. The result is often a bruise, torn hosiery or frayed tempers.
Since existing storm doors are designed to immediately begin closing at a controlled rate, it would be convenient to have a door closer which permits the door to remain almost completely open for a pre-determined period of time. This time period would be sufficiently long to allow the householder unrestricted activity through the doorway. It would be particularly convenient and advantageous to have this open time period pre-adjusted, thus avoiding the requirement of sliding the stopping means into place every time the door must be kept open.